1. Field of the Invention
The present invention relates to new compositions of new high frequency dielectric ceramics. More particularly, the present invention relates to compositions of high frequency dielectric ceramics having a high unloaded Q value (Qu) and low temperature sintering characteristics in a high frequency range such as micro- and millimeter wavelengths, as compared with the conventional compositions of ceramics.
2. Description of the Prior Art
Generally, compositions of dielectric ceramics are used as construction materials for dielectric resonators for stabilizing the frequency of band-pass filters, solid state oscillators, substrates, waveguides, antennas, and so on, in a high frequency range such as micro- and millimeter wavelengths. In recent years, rapid developments in integration technology of microwave circuits has led to an increasing need to develop dielectric ceramics for use in a high frequency range with high dielectric constants, low dielectric losses, and temperature stability at a resonant frequency with low production costs.
A wide variety of ceramic systems have been suggested as the high frequency dielectric ceramics. A representative example of such systems includes a BaO-TiO.sub.2 system, a ZrO.sub.2 -SnO.sub.2 -TiO.sub.2 system, a Perovskite system, and the like. However, most of the known systems show high dielectric losses when they are used in a high frequency range of above 10 GHz.
It has been reported that a complex Perovskite system having the formula of Ba(Mg.sub.1/3 Ta.sub.2/3)O.sub.3 shows good dielectric characteristics in a high frequency range. However, in order to obtain dielectric ceramics having a dielectric constant (K) of 23, an unloaded Q value (Qu) of 8,000, a temperature coefficient of resonant frequency (TCF) of 8 ppm/.degree.C. at 10.5 GHz, and a high sintering temperature of above 1,650.degree. C. should be achieved. Moreover, conventional systems cannot produce dielectric ceramics having a Qu more than 8,000 and a TCF less than 8 ppm/.degree.C. in a high frequency.